1. Field of the Invention
The invention relates generally to golf club heads and particularly to optimally proportioned golf club heads especially suited as irons.
2. Description of the Prior Art
The popularity of the game of golf likely resides in the virtual impossibility of mastering the game due to its technical complexity as well as the emotional factor brought about in part by the extraordinary difficulty of consistently striking the ball with accuracy and confidence. Over generations substantial improvements have come about in the tools used to play the game of golf, particularly the various clubs which include a group of clubs known as irons. A full set of golfing irons can include eleven separate irons which are usually numbered 1 through 9 with a "long" iron having a lower number. Such a set also includes a pitching wedge and a sand wedge. Irons include a head joined to a hosel and a shaft with the shaft being attached to the head by fitting the shaft into a bore formed in the hosel. The hosel is typically attached to and formed integrally with the head of an iron. It is conventional in the art for the head to include a heel, a bottom sole, a toe, a planar striking face and a back side.
The irons within a set of irons conventionally are formed to have varying degrees of loft angle and lie angle. The loft angle of an iron is that angle between a vertical plane, which includes the shaft, and the plane of the striking face of the iron. The lie angle of an iron is the angle between the shaft and the ground (horizontal plane) when the tangent to the sole directly under the center of mass is in the horizontal plane and when the shaft lies in a vertical plane. The loft angle of an iron determines how much loft is imparted to the ball when it is struck by the tilted striking face of the iron. The lie angle of the iron assures that when swung properly, the sole of the iron will contact the ground evenly so that the striking face will not tend to twist inwardly or outwardly and thereby ruin a shot made with the iron.
In a conventional set of irons, each iron has a number of horizontal grooves extending across the planar striking face. These horizontal grooves assist in imparting back spin to a golf ball when the ball is struck by the planar striking face. When the planar striking face fails to impart backspin to the ball, the ball may flutter and not fly an anticipated distance and will not hold or bite the playing surface of a course upon landing. For any set of golf irons, it is important that for a consistent swing, the iron impart consistant loft and distance to the ball. It is also important that when properly swung, the iron produces a consistent shot without a tendency to hook or slice.
Conventional golfing iron designs can be said to be either a traditional design wherein the iron is forged and has a generally continuous back portion on the club blade or of a second type wherein the design of the iron is referred to as a "cavity back" design wherein the back portion of the club blade includes a substantial depression or cavity which has the effect of providing perimeter weighting for the club head. Clubs of the "cavity back" style which include perimeter weighting have shown to provide a larger "sweet spot" or hitting area such that a ball need not be struck precisely in the center of mass of the club to produce an acceptable golf shot.
Golf clubs having oversize heads have also come to be known in the art and have been produced to the end of providing a greater sweet spot. Such "oversize" clubs do not preserve traditional head weights such as a player is comfortable with and typically do not provide a visual presentation to a player which promotes the confidence of the player. Player confidence is substantially improved when the player can consistently impact a golf ball on the "sweet spot" of a club. When a ball is not hit on the sweet spot of a golf club head, the club head will tend to twist from a position of being square with the intended flight path of the ball. The energy thus transferred to the golf ball is therefore less than maximum with a resultant loss in distance as well as a deviation from an ideal flight path.
The cavity back or perimeter weighted clubs referred to above as prior art club heads have intended to address the problem of off-center impact with a golf ball, that is, impact away from the sweet spot of the club head, so that the club head is forgiving, that is, the ball need not be struck precisely in the center of mass of the club to obtain an acceptable result. In a cavity back or perimeter weighted club, the club head is formed with a central hollow or cavity in the back surface of the club and material which would otherwise be located in the cavity is redistributed in predetermined proportions to strategic locations on the club head. A relatively large mass in such clubs is concentrated in the sole of the club in order to lower the center of gravity. A golfer therefore can more easily place the center of gravity of the club head below the center of gravity of the golf ball at the moment of impact for producing a properly airborn and solidly hit ball. Further, relatively large concentrations of mass are located in the heel and toe areas of a cavity back club in order to minimize the effects of hitting a golf ball on the toe or heel of the club head. When toe or heel hits occur, a club head will twist about the point of impact and result in less than a maximum transfer of energy to the golf ball at impact and deviations from the intended flight path of the ball. Such club heads are thus provided with relatively large concentrations of mass in the toe and heel areas of the club head so that the moment of inertia is increased and the golf club head will resist twisting movements in response to laterally off-centered hits.
Cavity back club structures have been provided by Solheim in U.S. Pat. No. 5,193,805, the club heads of Solheim having enlarged mass concentrations formed as protuberances at the heel and toe ends of a top ridge of the club head which extends longitudinally along the upper part of the head between the heel and toe ends of the head. U.S. Pat. No. 5,011,151 to Antonious discloses a club head having a mass referred to as a toe counterweight located above a theoretical longitudinal axis of the club head. The longitudinal axis is defined by Antonious as bisecting the face of the club head and is shown in the patent as extending between the heel and toe of the club head. The toe counterweight is a relatively large mass concentration which blends smoothly with the mass of the sole so that the counterweight appears to be an upwardly sweeping extension of the sole. In U.S. Pat. No. 5,209,473, Fisher describes golf irons wherein each blade includes a substantially planar face portion which is generally oval in shape and a back portion which is generally oval in shape and is disposed opposite the planar face portion. The back portion of the clubs of Fisher includes a cavity which is generally oval in shape with a torsion ring being provided which completely surrounds the the cavity and distributes the weight thereof around the perimeter of the cavity. Long, in U.S. Pat. Nos. 4,802,672 and 4,854,581 provides golfing irons which have progressively decreasing displacements between the axis of the shaft and the center of mass projected to a horizontal plane beginning with the long irons and progressing to the short irons. Each iron in a set provided by Long also has a support column behind the striking face, parabolic shaped horizontal grooves in the striking face, and a flat segment on the sole centered below the center of mass to cause the head to sit squarely at address. A still further example of a weighted iron club head is provided by Scheie et al in U.S. Pat. No. 5,224,705 wherein a golf club head is provided with a cavity having a pair of side walls which extend at certain angles to the hosel of the club head. The shape of cavity positions in the Scheie et al club heads positions a substantial portion of the weight of the heads in the upper portion of the toe of the head and in the lower portion of the heel of the head.
While substantial activity has occurred in the art with the intent of producing improved golfing club heads and particularly iron heads, the art has not provided an oversize iron head having a visual presentation which promotes player confidence and which provides an optimally distributed mass over the entire back side of the iron head, thereby producing an unusually large sweet spot such that player confidence is singularly promoted. Therefore, the present club heads address a long-felt need in the art by providing a new and improved club head and a new and improved set of club heads which address the needs of both the skilled golfer and the relatively unskilled golfer in their continuing attempts to master the game of golf.